PATHWAYS OF AERATION AND THE MECHANISMS AND BENEFICIAL-EFFECTS OF HUMIDITY-INDUCED AND VENTURI-INDUCED CONVECTIONS IN PHRAGMITES-AUSTRALIS (CAV) TRIN EX STEUD

The pathways of diffusive, humidity- and Venturi-induced convective ve ntilations in Phragmites australis (Cav.) Trin. ex Steud., and the mec hanisms of the convections are described. Experimental evidence, indic ating those factors, e.g. low relative humidity (RH), light, large lea f-sheath area, which increase humidity-induced convection; and those w hich increase Venturi convections, e.g. high wind speed, are reviewed. The superior aerating effects of convective as opposed to diffusive v entilation within the plant and their influence on the rhizosphere are demonstrated experimentally and by mathematical modelling.